Spacer chamfering gate stack scheme

ABSTRACT

A method of forming a gate structure for a semiconductor device that includes forming first spacers on the sidewalls of replacement gate structures that are present on a fin structure, wherein an upper surface of the first spacers is offset from an upper surface of the replacement gate structure, and forming at least second spacers on the first spacers and the exposed surfaces of the replacement gate structure. The method may further include substituting the replacement gate structure with a functional gate structure having a first width portion in a first space between adjacent first spacers, and a second width portion having a second width in a second space between adjacent second spacers, wherein the second width is greater than the first width.

BACKGROUND

Technical Field

The present disclosure relates to semiconductor devices, such assemiconductor devices including fin structures. The present disclosurefurther relates to processing of gate structures in fin includingstructures.

Description of the Related Art

The dimensions of semiconductor field effect transistors (FETs) havebeen steadily shrinking over the last thirty years or so, as scaling tosmaller dimensions leads to continuing device performance improvements.Planar FET devices typically have a conducting gate electrode positionedabove a semiconducting channel, and electrically isolated from thechannel by a thin layer of gate oxide. Current through the channel iscontrolled by applying voltage to the conducting gate. With conventionalplanar FET scaling reaching fundamental limits, the semiconductorindustry is looking at more unconventional geometries that willfacilitate continued device performance improvements. One such class ofdevice is a fin field effect transistor (finFET).

SUMMARY

In one aspect, a method of forming a gate structure for a semiconductordevice is provided that includes forming first spacers on the sidewallsof replacement gate structures that are present on a fin structure,wherein an upper surface of the first spacers is offset from an uppersurface of the replacement gate structure, and forming at least secondspacers on the first spacers and the exposed surfaces of the replacementgate structure. In some embodiments, the method further includessubstituting the replacement gate structure with a functional gatestructure having a first width portion in a first space between adjacentfirst spacers, and a second width portion having a second width in asecond space between adjacent second spacers, wherein the second widthis greater than the first width.

In another aspect, the present disclosure provides a semiconductordevice. In one embodiment, the semiconductor device may include a gatestructure present on a channel portion of a fin structure, the gatestructure including a first portion with a first width present on a gatedielectric, and a second portion with a second width present on thefirst portion, in which the second width is greater than the firstwidth. The semiconductor device may further include a composite spacer.The composite spacer may further include a first portion of a firstmaterial in contact with the first portion of the gate structure, and asecond portion of a second material in contact with the second portionof the gate structure.

In another aspect, the present disclosure provides a semiconductordevice. The semiconductor device may include an n-type finFET and ap-type finFET. The n-type finFET includes a first gate electrodecomprised of a titanium and carbon containing layer, a titanium andnitrogen containing layer and a tungsten fill present on a channelportion of a fin structure. The first gate electrode of the n-typefinFET may include a first portion with a first width present on a gatedielectric, and a second portion with a second width present on thefirst portion, in which the second width is greater than the firstwidth. The n-type finFET may further include a composite spacerincluding a first portion of a first material in contact with the firstportion of the first gate electrode, and a second portion of a secondmaterial in contact with the second portion of the first gate electrode.The p-type finFET includes a second gate electrode comprised of atitanium and nitrogen containing layer and a tungsten fill present on achannel portion of a fin structure. The second gate electrode of thep-type finFET includes a first portion with a first width present on agate dielectric, and a second portion with a second width present on thefirst portion, in which the second width is greater than the firstwidth. The p-type finFET may further include a composite spacerincluding a first portion of a first material in contact with the firstportion of the second gate electrode, and a second portion of a secondmaterial in contact with the second portion of the second gateelectrode.

BRIEF DESCRIPTION OF DRAWINGS

The following detailed description, given by way of example and notintended to limit the disclosure solely thereto, will best beappreciated in conjunction with the accompanying drawings, wherein likereference numerals denote like elements and parts, in which:

FIG. 1 is a side cross-sectional view that depicts forming a pluralityof replacement gate structures on a fin structure, in accordance withone embodiment of the present disclosure.

FIG. 2 is a side cross-sectional view that depicts forming first spacerson the sidewalls of replacement gate structures that are present on afin structure, in accordance with one embodiment of the presentdisclosure.

FIG. 3 is a side cross-sectional view that depicted forming asemiconductor material on the source and drain region portions of thefin structures, in accordance with one embodiment of the presentdisclosure.

FIG. 4 is a side cross-sectional view depicting recessing the firstspacers, in accordance with one embodiment of the present disclosure.

FIG. 5 is a side cross-sectional view depicting depositing a conformaloxide layer, in accordance with one embodiment of the presentdisclosure.

FIG. 6 is a side cross-sectional view depicting removing the horizontalsurfaces of the conformal oxide layer, in accordance with one embodimentof the present disclosure.

FIG. 7A is a side cross-sectional view depicting forming a conformalnitride layer on the structure depicted in FIG. 6, and removing thehorizontal surfaces of the conformal nitride layer, in accordance withone embodiment of the present disclosure.

FIG. 7B is a side cross-sectional view depicting forming a conformalnitride layer on the structure depicted in FIG. 6, in which thehorizontal surfaces of the conformal nitride layer are not removed fromthe structure, in accordance with another embodiment of the presentdisclosure.

FIG. 8 is a side cross-sectional view depicting forming an oxide fill onthe structure depicted in FIG. 7A, in accordance with one embodiment ofthe present disclosure.

FIG. 9 is a side cross-sectional view depicting removing the replacementgate structure, in accordance with one embodiment of the presentdisclosure.

FIG. 10 is a side cross-sectional view depicting forming a titanium andcarbon containing layer and an organic dielectric layer (ODL) in thegate region for an n-type FinFET and a p-type FinFET.

FIG. 11 is a side cross-sectional view depicting recessing the titaniumand carbon containing layer in the gate region of the n-type FinFET andthe p-type FinFET, in accordance with one embodiment of the presentdisclosure.

FIG. 12 is a side cross-sectional view depicting removing the titaniumand carbon containing layer from the gate region of the p-type FinFET,in accordance of one embodiment of the present disclosure.

FIG. 13 is a side cross-sectional view depicting forming a titanium andnitrogen containing layer in the gate region of the n-type FinFET andthe p-type FinFET, and forming a tungsten containing fill in the gateregion of the n-type FinFET and the p-type FinFET, in accordance withembodiment of the present disclosure.

FIG. 14 is a side cross-sectional view of a gate structure, inaccordance with one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “positioned on”means that a first element, such as a first structure, is present on asecond element, such as a second structure, wherein interveningelements, such as an interface structure, e.g. interface layer, may bepresent between the first element and the second element. The term“direct contact” means that a first element, such as a first structure,and a second element, such as a second structure, are connected withoutany intermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

In some embodiments, the present disclosure provides a spacer formingprocess flow that can generate openings for replacement gate processingsuitable for depositing work function metals for p-type and n-typesemiconductor devices, as well as the metal fill material for gateelectrodes. As used herein, “semiconductor device” refers to anintrinsic semiconductor material that has been doped, that is, intowhich a doping agent has been introduced, giving it different electricalproperties than the intrinsic semiconductor. Doping involves addingdopant atoms to an intrinsic semiconductor, which changes the electronand hole carrier concentrations of the intrinsic semiconductor atthermal equilibrium. Dominant carrier concentration in an extrinsicsemiconductor determines the conductivity type of the semiconductor,i.e., whether a semiconductor device is p-type or n-type. For example, asemiconductor device having p-type source and drain regions is typicallyreferred to as a p-type semiconductor device, and a semiconductor devicehaving n-type source and drain regions is typically referred to as ann-type semiconductor device. As used herein, a “p-type work functionmetal layer” is a metal layer that effectuates a p-type thresholdvoltage shift. In one embodiment, the work function of the p-type workfunction metal layer ranges from 4.9 eV to 5.2 eV. As used herein,“threshold voltage” is the lowest attainable gate voltage that will turnon a semiconductor device, e.g., transistor, by making the channel ofthe device conductive. The term “p-type threshold voltage shift” as usedherein means a shift in the Fermi energy of a p-type semiconductordevice towards a valence band of silicon in the silicon containingsubstrate of the p-type semiconductor device. A “valence band” is thehighest range of electron energies where electrons are normally presentat absolute zero. As used herein, an “n-type work function metal layer”is a metal layer that effectuates an n-type threshold voltage shift.“N-type threshold voltage shift” as used herein means a shift in theFermi energy of an n-type semiconductor device towards a conduction bandof silicon in a silicon-containing substrate of the n-type semiconductordevice. The “conduction band” is the lowest lying electron energy bandof the doped material that is not completely filled with electrons. Inone embodiment, the work function of the n-type work function metallayer ranges from 4.1 eV to 4.3 eV.

In some embodiments, FinFETs, such as those at the 14, 10 nm technologynodes, employ work-function metal chamfering process for desiredthreshold voltage (Vth). A field effect transistor (FET) is asemiconductor device in which output current, i.e., source-draincurrent, is controlled by the voltage applied to a gate structure to thesemiconductor device. A field effect transistor has three terminals,i.e., gate structure, source region and drain region. As used herein, a“fin structure” refers to a semiconductor material, which is employed asthe body of a semiconductor device, in which the gate structure ispositioned around the fin structure such that charge flows down thechannel on the two sidewalls of the fin structure and optionally alongthe top surface of the fin structure. A finFET is a semiconductor devicethat positions the channel region of the semiconductor device in a finstructure. In some examples, the nominal gate length (CD) of the FinFETcan be on the order of 20 nm, which can make it challenging forchamfering processing of the work function adjusting layers, i.e.,p-type work function metal layer and n-type work function metal layer,and subsequent metal fill process. Additionally, the width of the spacethat is provide by removing the replacement gate structure is greater atits base than at its opening, which can further complicate chamfering ofthe gate electrode. The methods and structures of the present disclosureare now discussed with more detail referring to FIGS. 1-14.

FIG. 1 depicts forming a plurality of replacement gate structures 10 ona fin structure 15. The fin structures 15 may be a plurality of siliconincluding fin structures that are formed from a semiconductor substrate1. In some embodiments, the plurality of silicon including finstructures 1 may be formed from a semiconductor on insulator (SOI)substrate (as depicted in FIG. 1) or a bulk semiconductor substrate.Referring to FIG. 1, the SOI substrate that may provide thesemiconductor substrate 1 may include at least a semiconductor oninsulator (SOI) layer (which is processed to provide the fin structures15) overlying a dielectric layer 3, in which a base semiconductor layer2 may be present underlying the dielectric layer 3. The dielectric layer3 may be referred to as a buried dielectric layer that can be composedof a nitride or oxide containing material. The base semiconductor layer2 may be composed of the same semiconductor material, or of a differentsemiconductor material, than the SOI layer that provides the finstructures 15. It is noted that in some embodiments it is not requiredthat the fin structures 15 be formed from an SOI substrate. For example,the dielectric layer 3 and the semiconductor layer that provides the finstructures 15 may be deposited on a bulk semiconductor substrate.

The fin structures 15 may be composed of a silicon containing material.For example, the fin structures 15 may be composed of a siliconcontaining material that may include, but is not limited to silicon,single crystal silicon, multicrystalline silicon, polycrystallinesilicon, amorphous silicon, strained silicon, silicon doped with carbon(Si:C), silicon germanium, silicon alloys or any combination thereof. Inone example, the fin structures 15 are composed of silicon (Si). The finstructures 15 may also be composed of other type IV semiconductors, suchas germanium (Ge), and compound semiconductor materials, such as typeIII/V semiconductor materials.

The plurality of fin structures 15 may be formed from the semiconductorsubstrate 1, e.g., SOI substrate, using photolithography and etchprocesses. Prior to etching the semiconductor substrate 1 to provide theplurality of fin structures 15, a layer of the dielectric material canbe deposited atop the SOI layer of the semiconductor substrate 1 toprovide a dielectric fin cap 20. The material layer that provides thedielectric fin cap 20 may be composed of a nitride, oxide, oxynitridematerial, and/or any other suitable dielectric layer. The dielectric fincap 20 may comprise a single layer of dielectric material or multiplelayers of dielectric materials. The material layer that provides thedielectric fin cap 20 can be formed by a deposition process, such aschemical vapor deposition (CVD) and/or atomic layer deposition (ALD).Alternatively, the material layer that provides the dielectric fin cap20 may be formed using a growth process, such as thermal oxidation orthermal nitridation. The material layer that provides the dielectric fincap 20 may have a thickness ranging from 1 nm to 100 nm.

In one embodiment, following the formation of the layer of dielectricmaterial that provides the dielectric fin cap 20, a photolithography andetch process sequence is applied to the material layer for thedielectric fin cap 20 and the portion of the semiconductor substrate 1that provides the fin structures 15. Specifically, in one example, aphotoresist mask 21 is formed overlying the layer of the dielectricmaterial that provides dielectric fin cap 20, in which the portion ofthe dielectric material that is underlying the photoresist mask 21provides the dielectric fin cap 20, and the portion of the SOI layer ofthe SOI substrate that is underlying the photoresist mask 21 providesthe plurality of fin structures 15. The exposed portions of thedielectric material that provides dielectric fin cap 20, that is notprotected by the photoresist mask 21, are removed using a selective etchprocess. The selective etch process may be a directional etch,anisotropic etch, such as reactive ion etching (RIE). Followingpatterning of the dielectric fin cap 20, at least a portion of thesubstrate 1 is etched to form the plurality of fin structures 15.

Each of the fin structures in the plurality of fin structures 15 mayhave a height ranging from 5 nm to 200 nm. In another embodiment, eachof the plurality of fin structures 15 has a height ranging from 10 nm to100 nm. In one example, each of the plurality of fin structures 15 has aheight ranging from 20 nm to 50 nm. Each of the plurality of finstructures 15 may have a width of less than 20 nm. In anotherembodiment, each of the plurality of fin structures 15 has a widthranging from 3 nm to 8 nm. The pitch separating adjacent fin structuresin the plurality of fin structures 15 may range from 10 nm to 500 nm. Inanother example, the pitch separating adjacent fin structures in theplurality of fin structures 15 is 60 nm.

A plurality of replacement gate structures 10 are present on the finstructures 15. As used herein, the term “replacement gate structure 10”denotes a sacrificial structure that dictates the geometry and locationof the later formed functioning gate structure. The “functional gatestructure” functions to switch the semiconductor device from an “on” to“off” state, and vice versa. In one embodiment, the replacement gatestructure 10 includes an interfacial dielectric material (not shown),and a sacrificial gate material 19. In one embodiment, the sacrificialmaterial that provides the sacrificial gate material 19 may be composedof any material that can be etched selectively to the at least one finstructure 15. In one embodiment, the sacrificial gate material 19 may becomposed of a silicon-including material, such as polysilicon. Inanother embodiment, the sacrificial gate material 19 may be composed ofa dielectric material, such as an oxide, nitride or oxynitride material,or amorphous carbon. The sacrificial gate material 19 may be formedusing deposition (e.g., chemical vapor deposition) photolithography andetch processes (e.g., reactive ion etching). Although FIG. 1 depictsfive replacement gate structures 10, the present disclosure is notlimited to only this example. In some embodiments, the pitch, i.e.,center to center distance, separating adjacent replacement gatestructures 15 may range from 20 nm to 10 nm.

FIG. 2 depicts one embodiment of forming first spacers 25 on thesidewalls of replacement gate structures 10 that are present on the finstructures 15. Forming the first spacers 25 may begin with depositing afirst dielectric layer using a deposition process, such as chemicalvapor deposition (CVD). Variations of CVD processes suitable for formingthe first dielectric layer include, but are not limited to, AtmosphericPressure CVD (APCVD), Low Pressure CVD (LPCVD) and Plasma Enhanced CVD(PECVD), Metal-Organic CVD (MOCVD) and combinations thereof may also beemployed. The first dielectric layer is typically a conformal layer. Theterm “conformal” denotes a layer having a thickness that does notdeviate from greater than or less than 30% of an average value for thethickness of the layer. The first dielectric layer may be composed of anitride containing dielectric, such as silicon nitride, an oxidecontaining dielectric, such as silicon oxide, or a combination thereof.In one example, the first dielectric layer that is processed to providethe first spacers 25 is composed of silicon carbon boron nitride(SiCBN). In one embodiment, the thickness of the first dielectric layertypically ranges from 4 nm to 20 nm. In another embodiment, thethickness of the first dielectric layer ranges from 4 nm to 10 nm.

Following the deposition of the first dielectric layer, an etch processmay be employed to remove the horizontal portions of the firstdielectric layer, wherein the remaining vertical portions of the firstdielectric layer provide the first spacers 25. The first spacers 25 arepresent in direct contact with the sidewalls of the sacrificial gatestructure 10. The horizontal portions of the first dielectric layer canbe removed from the fin structures 15 and the upper surface of thedielectric layer 2 of the substrate 1. The horizontal portions of thefirst dielectric layer may be removed by an anisotropic etch process,such as reactive ion etching (RIE). As used herein, an “anisotropic etchprocess” denotes a material removal process in which the etch rate inthe direction normal to the surface to be etched is greater than in thedirection parallel to the surface to be etched. Other examples ofanisotropic etching that can be used at this point of the presentinvention include ion beam etching, plasma etching or laser ablation.

In some embodiments, the width of the first spacers 25 may range from 2nm to 25 nm, as measured from the sidewall of the sacrificial gatestructure 10. In another embodiment, the width of the first spacers 25may range from 4 nm to 10 nm, as measured from the sidewall of thesacrificial gate structure 10.

FIG. 3 depicts forming a semiconductor material 30 on the source anddrain region portions of the fin structures 15. The semiconductormaterial 30 may be epitaxially formed and may be in situ doped with ann-type or p-type dopant, and may provide at least one doped portion ofthe source and drain regions of the FinFETs. As used herein, the term“drain” means a doped region in semiconductor device located at the endof the channel region, in which carriers are flowing out of thetransistor through the drain. The term “source” is a doped region in thesemiconductor device, in which majority carriers are flowing into thechannel region. The terms “epitaxial growth and/or deposition” and“epitaxially formed” mean the growth of a material, such as asemiconductor or dielectric, on a deposition surface of a semiconductormaterial, in which the material being grown has the same crystallinecharacteristics as the semiconductor material of the deposition surface.A material referred to as being an “epitaxial” material is a materialformed using an epitaxial deposition process, and has the samecrystalline structure as the material the epitaxial material is formedon. Epitaxial deposition may also provide a selective depositionprocess, as the epitaxially deposited semiconductor material may only beformed on other semiconductor materials, e.g., the epitaxial material isnot formed on dielectric surfaces. By “in-situ” it is meant that thedopant that dictates the conductivity type of the epitaxially formed insitu doped source and drain region structures 30 a, 30 b is introducedduring the process step, e.g., epitaxial deposition, which forms theepitaxially formed in situ doped source and drain region structures 30a, 30 b.

In some embodiments, the epitaxial semiconductor material 30 that isformed on the source and drain portions of the fin structures 15 forp-type FinFETs is silicon germanium. In some embodiments, the epitaxialsemiconductor material 30 that is formed on the source and drainportions of the fin structures 15 for n-type FinFETs is silicon. Anumber of different sources may be used for the deposition of thesemiconductor material that forms the raised source/drain regions 36. Insome embodiments, in which the epitaxial semiconductor material 30 iscomposed of silicon, the silicon gas source for epitaxial deposition maybe selected from the group consisting of hexachlorodisilane (Si₂Cl₆),tetrachlorosilane (SiCl₄), dichlorosilane (Cl₂SiH₂), trichlorosilane(Cl₃SiH), methylsilane ((CH₃)SiH₃), dimethylsilane ((CH₃)₂SiH₂),ethylsilane ((CH₃CH₂)SiH₃), methyldisilane ((CH₃)Si₂H₅),dimethyldisilane ((CH₃)₂Si₂H₄), hexamethyldisilane ((CH₃)₆Si₂) andcombinations thereof. In some embodiments, in which epitaxialsemiconductor material 30 is composed of silicon germanium, the siliconsources for epitaxial deposition may be selected from the groupconsisting of silane, disilane, trisilane, tetrasilane,hexachlorodisilane, tetrachlorosilane, dichlorosilane, trichlorosilane,methylsilane, dimethylsilane, ethylsilane, methyldisilane,dimethyldisilane, hexamethyldisilane and combinations thereof, and thegermanium gas sources may be selected from the group consisting ofgermane, digermane, halogermane, dichlorogermane, trichlorogermane,tetrachlorogermane and combinations thereof.

In some embodiments, the epitaxially formed in situ doped semiconductormaterial 30 is merging source and drain region structures, in which asingle continuous portion of in situ doped epitaxial semiconductormaterial are in direct contact with the source and drain region portionsof adjacent fin structures 15. Embodiments have also been contemplatedin which the epitaxial semiconductor material on the source and drainregion portions of the fin structures in an n-type device region areseparated from the epitaxial semiconductor material on the source anddrain region portions of the fin structures in a p-type device region.In some examples, this may be referred to as source and drain regionsthat are composed of unmerged epitaxy.

In some embodiments, the extension source and drain regions may beformed after the epitaxially formed in situ doped semiconductor material30 is positioned on the source and drain region portions of the finstructures 15 by thermally diffusing the n-type or p-type dopant fromthe epitaxially formed in situ doped semiconductor material 30 into theunderlying portion of the fin structures 15. In some embodiments, thesource and drain regions are activated by a high temperature anneal.

FIG. 4 depicts recessing the first spacers 25. The first spacers 25 maybe recessed using an anisotropic etch process. Examples of anisotropicetching that can be used at this point of the present disclosure includereactive ion etching, ion beam etching, plasma etching or laserablation. The etch process for recessing the first spacers 25 mayinclude a selective etch chemistry that does not substantially etch atleast the semiconductor material 30. In some embodiments, followingrecessing, the first spacers 25 may have a height, i.e., recessedheight, ranging from 5 nm to 35 nm, as measured from the upper surfaceof the dielectric layer 3. In some embodiments, following recessing, thefirst spacers 35 may have a height, i.e., recessed height, ranging from10 nm to 30 nm, as measured from the upper surface of the dielectriclayer 3. The height, i.e., recessed height, of the first spacer 25 istypically approximate to the height of the upper surface of thesemiconductor material 30. The portion of the sidewall of thereplacement gate structure 10 that the first spacer 25 is in contactwith may be referred to as the lower portion of the replacement gatestructure 10.

FIGS. 5 and 6 depict one embodiment of forming a second spacer 35 on anupper portion of the replacement gate structure 10. The second spacer 35is typically composed of an oxide containing dielectric. For example,the second spacer 35 may be composed of silicon oxide, aluminum oxide,silicon oxynitride, hafnium oxide or a combination thereof. In oneexample, when the first spacer 25 is composed of silicon carbon boronnitride (SiBCN), the second spacer 35 may be composed of silicon oxide(SiO₂). It is noted that this is only one example of a material that issuitable for the second spacer 35. The second spacer 35 may be composedof any dielectric material that provides that the replacement gatestructure 10 can be removed using a selective etch process.

In some embodiments, forming the second spacer 35 may begin withdepositing a conformal second dielectric layer 35 a on the replacementgate structures 10, as depicted in FIG. 5. The second dielectric layer35 a can be formed using a chemical vapor deposition (CVD) process,which can include atmospheric pressure CVD (APCVD), low pressure CVD(LPCVD), plasma enhanced CVD (PECVD), metal-organic CVD (MOCVD) andcombinations thereof. The second dielectric layer 35 a is typicallycomposed of an oxide containing dielectric, such as silicon oxide, butother dielectric materials may be equally suitable, such as nitrides andoxynitrides. In one embodiment, the thickness of the second dielectriclayer 35 a typically ranges from 4 nm to 20 nm. In another embodiment,the thickness of the second dielectric layer 35 a ranges from 4 nm to 10nm.

Following the deposition of the second dielectric layer 35 a, an etchprocess may be employed to remove the horizontal portions of the seconddielectric layer 35 a, wherein the remaining vertical portions of thesecond dielectric layer 35 a provide the second spacers 35, as depictedin FIG. 6. The second spacers 35 are present in direct contact with theupper sidewalls of the sacrificial gate structure 10. The horizontalportions of the second dielectric layer can be removed from thesemiconductor material 30 by an anisotropic etch process, such asreactive ion etching (RIE). Other examples of anisotropic etching thatcan be used at this point of the present disclosure include ion beametching, plasma etching or laser ablation.

In some embodiments, the width of the second spacers 35 may range from 4nm to 20 nm, as measured from the sidewall of the sacrificial gatestructure 10. In another embodiment, the width of the second spacers 35may range from 4 nm to 10 nm, as measured from the sidewall of thesacrificial gate structure 10.

FIGS. 7A and 7B depict forming a third spacer 40 a, 40 b on thestructure depicted in FIG. 6. In the embodiment that is depicted in FIG.7A, the third spacer 40 a is only present on the sidewall of the secondspacer 35, and optionally the sidewall of the first spacer 25. In theembodiment depicted in FIG. 7B, the third spacer 40 b includes a firstportion, i.e., vertically orientated portion, that is present alongsubstantially an entirety of the sidewall of the second spacer 35, andincludes a second portion, i.e., horizontally orientated portion, thatextends over the upper surface of the semiconductor material 30.

In one embodiment, the third spacer 40 a is formed by conformallydepositing a third dielectric layer on the structure depicted in FIG. 6followed by an anisotropic etch to remove the horizontal portions of thethird dielectric layer, wherein the vertical portions of the thirddielectric layer remain on the sidewalls of the second spacer 35 toprovide the third spacer 40 a. The third dielectric layer is typically aconformal layer that is formed using a chemical vapor depositionprocess, such as atmospheric pressure CVD (APCVD), low pressure CVD(LPCVD), plasma enhanced CVD (PECVD), metal-organic CVD (MOCVD) andcombinations thereof. The third dielectric layer may be composed of anitride. For example, when the first spacer 25 is composed of siliconboron carbon nitride (SiBCN), and the second spacer 35 is composed ofsilicon oxide (SiO₂), the third dielectric layer that provides the thirdspacer 40 a may be silicon nitride (Si₃N₄). Following deposition, thethird dielectric layer may be etched with an anisotropic etch, such asreactive ion etch (RIE), ion beam etching, plasma etching or laserablation, to remove the horizontal portions, as depicted in FIG. 7A. Thethird dielectric layer may be deposited to a thickness to provide athird spacer 40 a having a width ranging from 4 nm to 20 nm, and in someembodiments ranging from 4 nm to 10 nm, as measured from the sidewall ofthe sacrificial gate stack 10. FIG. 7B depicts another embodiment of thethird spacer 35 b in which the horizontal portions of the thirddielectric layer where not remove. To provide this embodiment of thethird spacer 35 b, the anisotropic etch step is omitted from the processsequence described with reference to FIG. 7A. It is noted that althoughthe remainder of the process flow, e.g., FIGS. 8-9, that are describedherein includes the embodiment of the third spacer 40 a that is depictedin FIG. 7A, the third spacer 40 b depicted in FIG. 7B is equallyapplicable to the following description.

FIG. 8 depicts one embodiment of forming a fill dielectric 45 on thestructure depicted in FIG. 7A. The fill dielectric 45 may be selectedfrom the group consisting of silicon-including materials such as SiO₂,SiN, Si₃N₄, SiO_(X)N_(y), SiC, SiCO, SiCOH, and SiCH compounds; theabove-mentioned silicon including materials with some or all of the Sireplaced by Ge; carbon-doped oxides; inorganic oxides; inorganicpolymers; hybrid polymers; organic polymers such as polyamides or SiLK™;other carbon-containing materials; organo-inorganic materials such asspin-on glasses and silsesquioxane-based materials; and diamond-likecarbon (DLC, also known as amorphous hydrogenated carbon, α-C:H). Thefill dielectric 45 may be deposited using at least one of spinning fromsolution, spraying from solution, chemical vapor deposition (CVD),plasma enhanced CVD (PECVD), sputter deposition, reactive sputterdeposition, ion-beam deposition, and evaporation. Following depositionof the fill dielectric 45, a planarization processes is conducted sothat the upper surface of the fill dielectric 45 is coplanar with theupper surface of the replacement gate structure 10. The planarization ofthe dielectric material 45 may be provided by chemical mechanicalplanarization.

FIG. 9 depicts one embodiment of removing the replacement gate structure10 to expose a channel region portion of the plurality of fin structures15. In some embodiments, the replacement gate structure 10 may beremoved by a selective etch process. The replacement gate structure 10may be removed using a wet or dry etch process. In one embodiment, thereplacement gate structure 10 is removed by reactive ion etch (RIE). Inone example, an etch step for removing the replacement gate structure 10can include an etch chemistry for removing the replacement gatestructure 10 selective to the plurality of fin structures 15. Removingthe replacement gate structure 10 forms a functional gate structurespace 50 that leads to the channel portion of the fin structures 15.

In some embodiments, following removal of the replacement gate structure10, the second spacer 35 may be removed. In some examples, the secondspacer 35 may be removed by an etch process that is selective to atleast the first spacer 25 and the third spacer 40 a. The selective etchprocess for removing the second spacer 35 may also be selective to thefin structures 15 and the fill dielectric 45. Removing the second spacer35 increases the opening width W2 of the functional gate structure space50 at its opening relative to the width W1 of the functional gatestructure space 50 at its base. For example, the width W2 of the openingto the gate structure space 50 may range from 5 nm to 25 nm, and thewidth W1 of the gate structure space 50 at its base may range from 2 nmto 15 nm. In another example, the width W2 of the opening to the gatestructure space 50 may range from 10 nm to 20 nm, and the width W1 ofthe gate structure space 50 at its base may range from 5 nm to 10 nm.The geometry of the gate structure space 50 having a greater width atits opening W2 relative to its base W1 is referred to herein as a gatestructure space 50 that is T-shaped.

A functional gate structure that is formed in the gate structure space50 that is T-shaped is also referred to herein as being a T-shapedfunctional gate structure. A T-shaped functional gate structure having asmall gate length that is provided by the narrow width of the baseportion of the T-shaped gate structure, and having a relaxed criticaldimension (CD) provided by a greater width at the upper portion of theT-shaped gate structure, provides an enhanced process window for workfunction metal chamfering process steps.

FIGS. 10-13 depict one embodiment for forming a functional gatestructure 55 in the opening that is formed by removing the replacementgate structure. FIGS. 10-13 depict the gate electrode 60 a, 60 b of afunctional gate structure being formed in a gate structure space 50 thatis formed in accordance with the process flow depicted in FIGS. 1-9. Thegate dielectric (not shown) for the functional gate structure can beformed prior to forming the gate electrode 60 a, 60 b, and is formed onthe channel region portion of the fin structures 15. The gate dielectricmay be a dielectric material, such as SiO₂, or alternatively high-kdielectrics, such as oxides of Hf, Ta, Zr, Al or combinations thereof.In another embodiment, the at least one gate dielectric is comprised ofan oxide, such as SiO₂ or HfO₂. The gate electrode 60 a, 60 b is formedwithin the gate structure space 50 atop the gate dielectric.

In the embodiments depicted in FIGS. 10-13, a gate electrode 60 a havinga combination of work function metals for providing a n-type FinFET isdepicted being formed on one fin structure, and a gate electrode 60 bhaving a combination of work function metals for providing a p-typeFinFET is depicted being formed on a second fin structure. In theembodiments described with reference to FIGS. 10-13, the gate electrode60 a for the n-type FinFET may be composed of a titanium and carboncontaining layer 61 a, e.g., titanium carbide (TiC) layer, being formedon the gate dielectric; a titanium and nitride containing layer 62 a,e.g., titanium nitride (TiN), being formed on titanium and carboncontaining layer 61 a; and a metal fill 63 a, e.g., tungsten (W) fill,being formed on the titanium and nitride containing layer 62 a. In theembodiments described with reference to FIGS. 10-13, the gate electrode60 b for the p-type FinFET may be composed of a titanium and nitrogencontaining layer 62 b, e.g., titanium nitride (TiN) layer, being formedon the gate dielectric; and a metal fill 63 b, e.g., tungsten (W) fill,being formed on the titanium and nitride containing layer 62 b.

FIG. 10 depicts one embodiment of forming a titanium and carboncontaining layer 61 a, 61 b, e.g., titanium carbide (TiC), and anorganic dielectric layer (ODL) 64 in the gate structure space 50 for ann-type FinFET and a p-type FinFET. The titanium and carbon containinglayer 61 a, 61 b, e.g., titanium carbide (TiC) layer, may be depositedwithin the gate structure space 50 on the gate dielectric at the base ofthe opening using atomic layer deposition. The titanium and carboncontaining layer 61 a, 61 b, e.g., titanium carbide (TiC) layer, istypically deposited as a conformal layer and may be formed directly onthe sidewalls of the gate structure space 50 that is provided by thefirst spacer 25 and the third spacer 40 a, 40 b. In one embodiment, thethickness of the titanium and carbon containing layer 61 a, 61 b mayrange from 3 nm to 10 nm. In another example, the thickness of thetitanium and carbon containing layer 61 a, 61 b may range from 5 nm to 8nm. The titanium and carbon containing layer 61 a, 61 b may be depositedusing atomic layer deposition (ALD). The organic dielectric layer 64 maybe deposited using a spin on dielectric method, or may alternatively bedeposited using chemical vapor deposition. The organic dielectric layer64 is typically deposited to fill the lower portion of the gatestructure space 50. In some embodiments, the organic dielectric layer 64may be recessed within the gate structure space 50 using an etchprocess.

FIG. 11 depicts recessing the titanium and carbon containing layer 61 a,61 b in the gate structure space 50 of the n-type FinFET and the p-typeFinFET. The titanium and carbon containing layers 61 a, 61 b may berecessed so that the upper surface of the titanium and carbon containinglayers 61 a, 61 b are substantially coplanar with the upper surface ofthe organic dielectric layer 64 that are present in the lower portion ofthe gate structure space 50.

FIG. 12 depicting removing the titanium and carbon containing layer fromthe gate region of the p-type FinFET. During this process step, theorganic dielectric layer 64 is removed from the gate structure space 50of both the n-type FinFET and the p-type FinFET. In some embodiments, anetch mask, e.g., photoresist mask, may be formed over the titanium andcarbon containing layer 61 a that is present in then n-type FinFETportion of the substrate, which the titanium and carbon containing layer61 b is removed from the p-type FinFET portion of the substrate.

FIG. 13 depicting forming a titanium and nitrogen containing layer 62 a,62 b, e.g., titanium nitride (TiN) layer, in the gate region of then-type FinFET and the p-type FinFET, and forming a tungsten containingfill 63, e.g., tungsten (W) fill, in the gate region of the n-typeFinFET and the p-type FinFET. The titanium and nitrogen containing layer62 a, 62 b, e.g., titanium nitride (TiN) layer, is typically depositedas a conformal layer and may be formed directly on the sidewalls of thegate structure space 50 that is provided by the first spacer 25 and thethird spacer 40 a, 40 b. For the p-type FinFET the titanium and nitrogencontaining layer 62 b may be deposited into direct contact with the gatedielectric that is within the gate structure space 50. For the n-typeFinFET, the titanium and nitrogen containing layer 62 a may be depositedto fill the opening between the vertical portions of the titanium andcarbon containing layer 61 a. In one embodiment, the thickness of thetitanium and nitrogen containing layer 62 a, 62 b may range from 3 nm to10 nm. In another example, the thickness of the titanium and nitrogencontaining layer 62 a, 62 b may range from 5 nm to 8 nm. Following theformation of the titanium and nitrogen containing layer 62 a, 62 b, thetungsten containing fill 63, e.g., tungsten (W) fill, is deposited inthe gate region of the n-type FinFET and the p-type FinFET. The tungstencontaining fill 63 may be deposited using plating.

FIG. 14 depicts one embodiment of a semiconductor device in accordancewith the present disclosure. In some embodiments, the semiconductordevice depicted in FIG. 14 may be a FinFET. FIG. 14 depicts asemiconductor device that includes a gate structure 500 present on achannel portion of a fin structure 15, the gate structure 500 includinga first portion with a first width W1 present on a gate dielectric (notshown), and a second portion with a second width W2 present on the firstportion, in which the second width W2 is greater than the first widthW1. The semiconductor device, e.g., FinFET, may further include acomposite spacer 25, 40 b including a first portion 25 of a firstmaterial in contact with the first portion of the gate structure, and asecond portion 40 b of a second material in contact with the secondportion of the gate structure.

In some embodiments, the first width W1 of the first width portion ofthe gate structure ranges from 15 nm to 20 nm, and the second width W2of the second width portion of the gate structure ranges from 20 nm to30 nm. In some embodiments, the first material 25 of the compositespacer comprises a silicon boron carbon nitride (SiBCN) material, andthe second material 140 b of the composite spacer may be composed of anitride, such as silicon nitride. The fill portion 45 of the secondspacer is comprised of a oxide, such as silicon oxide.

The gate structure 500 depicted in FIG. 14 include the gate electrode 55a of an n-type FinFET as depicted in FIG. 13, or may include the gateelectrode 55 b of the p-type FinFET as depicted in FIG. 13.

While the methods and structures of the present disclosure have beenparticularly shown and described with respect to preferred embodimentsthereof, it will be understood by those skilled in the art that theforegoing and other changes in forms and details may be made withoutdeparting from the spirit and scope of the present disclosure. It istherefore intended that the present disclosure not be limited to theexact forms and details described and illustrated, but fall within thescope of the appended claims.

What is claimed is:
 1. A semiconductor device comprising: a gatestructure present on a channel portion of a fin structure, the gatestructure including a material stack of a titanium and carbon layerhaving a single U-shaped geometry on a gate dielectric, a titanium andnitrogen layer having a dual U-shaped geometry present on the titaniumand carbon layer, wherein a lower U-shaped geometry portion fills anopening in the single U-shaped geometry of the titanium and carbonlayer, an upper U-shaped geometry portion of the titanium and nitrogenlayer having a greater with than the lower U-shaped geometry portion,and a tungsten containing fill present on the titanium and nitrogenlayer; and a composite spacer including a first portion of a firstmaterial a second portion of a second material in contact with thesecond portion of the gate structure.
 2. The semiconductor device ofclaim 1, wherein first material comprises silicon boron carbon nitride(SiBCN).
 3. The semiconductor device of claim 1, wherein the secondportion of the composite spacer comprises a conformal portion and a fillportion.
 4. The semiconductor device of claim 3, wherein the conformalportion of the second spacer is comprised of an oxide.
 5. Thesemiconductor device of claim 4, wherein the fill portion of the secondspacer is comprised of a nitride.
 6. A semiconductor device comprising:a gate structure present on a channel portion of a fin structure, thegate structure including a material stack of a titanium and carbon layerhaving a single U-shaped geometry on a gate dielectric, a titanium andnitrogen layer having a dual U-shaped geometry present on the titaniumand carbon layer, wherein a lower U-shaped geometry portion fills anopening in the single U-shaped geometry of the titanium and carbonlayer, an upper U-shaped geometry portion of the titanium and nitrogenlayer having a greater with than the lower U-shaped geometry portion,and a tungsten containing fill present on the titanium and nitrogenlayer; and a composite spacer including a first portion of a firstmaterial comprising silicon boron carbon nitride (SiBCN), and a secondportion of a second material in contact with the second portion of thegate structure.
 7. The semiconductor device of claim 6, wherein thesecond portion of the composite spacer comprises a conformal portion anda fill portion.
 8. The semiconductor device of claim 7, wherein theconformal portion of the second spacer is comprised of an oxide.
 9. Thesemiconductor device of claim 8, wherein the fill portion of the secondspacer is comprised of a nitride.
 10. A semiconductor device comprising:a gate structure present on a channel portion of a fin structure, thegate structure including a first portion with a first width present on agate dielectric, and a second portion with a second width present on thefirst portion, in which the second width is greater than the firstwidth, wherein a material stack of a titanium and carbon layer having asingle U-shaped geometry on a gate dielectric, a titanium and nitrogenlayer having a dual U-shaped geometry present on the titanium and carbonlayer, wherein a lower U-shaped geometry portion fills an opening in thesingle U-shaped geometry of the titanium and carbon layer, an upperU-shaped geometry portion of the titanium and nitrogen layer having agreater with than the lower U-shaped geometry portion, and a tungstencontaining fill present on the titanium and nitrogen layer; and acomposite spacer including a first portion of a first materialcomprising silicon boron carbon nitride (SiBCN) in contact with thefirst spacer portion of the gate structure, and a second portion of asecond material in contact with the second spacer portion of the gatestructure, wherein the second spacer portion includes a conformal layercomponent and a fill component.
 11. The semiconductor device of claim10, wherein the conformal component of the second spacer portion iscomprised of an oxide.
 12. The semiconductor device of claim 11, whereinthe oxide of the second spacer portion is composed of silicon oxide. 13.The semiconductor device of claim 10, wherein the fill portion of thesecond spacer is comprised of a nitride.
 14. The semiconductor device ofclaim 13, wherein the nitride of the fill portion is composed of siliconnitride.